Culegere de probleme de Analiz˘a numeric˘a
Culegere de probleme de Analiz˘a numeric˘a
Culegere de probleme de Analiz˘a numeric˘a
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
9.3. Alte formule <strong>de</strong> tip interpolator 133<br />
b<br />
A1j =<br />
a<br />
h1j(x)dx =<br />
= s(s−1)...(s−j) (b−a)j+1<br />
·<br />
2s(2s−1)...(2s−j) (j +1)!<br />
b<br />
a<br />
s j x−a (x−b)<br />
b−a j!<br />
f ∈ C 2s [a,b] ⇒ R2s−1(f) =<br />
n−j <br />
<br />
n+ν x−b<br />
dx = (−1)<br />
ν a−b<br />
j A0j<br />
ν=0<br />
2 2s+1 s! (b−a)<br />
f<br />
(2s)! 2s+1<br />
(2s) (ξ)<br />
<br />
K2s−1 = (b−t)2s<br />
(2s)! −<br />
s−1<br />
A1j<br />
j=0<br />
= 1<br />
(2s)! (b−t)s (s−t) s<br />
(b−t) 2s−j−1<br />
(2s−j −1)! =<br />
K2s−1(t) are semn constant pe [a,b], iar f (2s) este continuă s¸i se poate aplica<br />
formula <strong>de</strong> medie sau corolarul la teorema lui Peano.<br />
Problema 9.3.3 Stabilit¸i o formulă <strong>de</strong> cuadratură <strong>de</strong> forma<br />
b<br />
a<br />
f(x)dx = Af ′ (a)+Bf(b)+R1(f)<br />
Solut¸ie. Pornim <strong>de</strong> la formula <strong>de</strong> interpolare <strong>de</strong> tip Birkhoff<br />
Integrând se obt¸ine<br />
f(x) = (x−b)f ′ (a)+f(b)+(R1f)(x)<br />
int b <br />
a−b<br />
af(x)dx = (b−a)<br />
2 f′ <br />
(a)+f(b) +R1(f)<br />
Pentru rest se aplică teorema lui Peano s¸i se ajunge în final la<br />
R1(f) = − (b−a)3<br />
f<br />
3<br />
′′ (ξ), ξ ∈ [a,b].<br />
Problema 9.3.4 Deducet¸i o formulă <strong>de</strong> cuadratură integrând formula <strong>de</strong> aproximare<br />
a lui Bernstein.